So today I hooked up the TT for the first time this season and while checking the lights, I hear a high pitched squeal coming from all four brakes (truck is idling BTW). I checked the Prodigy and it's happily indicating ".c.". So I plug and unplug the 7 pin a couple of times and it quits. I get to the shop and when I walk back to the TT, the brakes are squealing again! Note the truck is off at this point. I checked the TT brakes and they were not hot like from dragging. The contacts at the 7 pin are fair (no corrosion) but could use some cleaning.
Whats all the squealing??

Yup, the PP tanks were off the trailer and sitting in the back yard. The emergency switch was OK - or at least it was together. The brakes worked normally all the way to the shop (about 6 miles). Trailer is going in for a repaint of its front cap ~ maybe it was scared!
I'm wondering if my 7 pin is just cruddy enough to have some resistance to it or something.